README.md

Realtime Clock

The RTC devices supported by the project include DS1307, DS3231, PCF8563.

A class for setting the system clock is also provided, so that for instance the Raspberry Pi's operating system time can be synchronized to a hardware RTC clock.

Documentation

• DS1307 datasheet
• DS3231 datasheet
• PCF8563 datasheet

Board

Usage with Hardware clocks

Hardware Required

• DS1307/DS3231/PCF8563
• Male/Female Jumper Wires

I2cConnectionSettings settings = new I2cConnectionSettings(1, Ds1307.DefaultI2cAddress);
I2cDevice device = I2cDevice.Create(settings);

using (Ds1307 rtc = new Ds1307(device))
{
    // set DS1307 time
    rtc.DateTime = DateTime.Now;

    // loop
    while (true)
    {
        // read time
        DateTime dt = rtc.DateTime;

        Console.WriteLine($"Time: {dt.ToString("yyyy/MM/dd HH:mm:ss")}");
        Console.WriteLine();

        // wait for a second
        Thread.Sleep(1000);
    }
}

Result

Setting the operating system clock

The class SystemClock contains static methods to set the operating system clock. Since this operation requires elevated permissions, some special requirements apply unless the application is run as root (on Linux or MacOs)/administrator (on Windows).

On linux or MacOs, the user calling the SetSystemTimeUtc must either be root or the date command must have the setUid bit set. To do this, one must execute this command once: sudo chmod +s /bin/date. This allows everyone to set the clock.

On Windows, a system policy exists to allow anybody of a named user group to set the system clock. Normally, this right is limited to users belonging to the "Administrators" group. To configure it, open 'gpedit.msc' and go to Computer Configuration > Windows Settings > Security Settings > Local Policies > User Rights Assignments and add the user or his group to the setting 'Change System Time'.